Abstract

One of the limitations of using hobbyist remotely controlled aircraft with an attached digital camera is that a great number of images look alike and unless a large number of natural features or artificial targets are present at the location, it was hard to identify and orientate the images.
This paper investigates the use of an unmanned aerial vehicle (UAV) for use in agricultural applications. Trials were conducted, in collaboration with researchers from the Australian Research Centre for Aerospace Automation (ARCAA) - Queensland University of Technology (QUT), on the ability of the UAV autopilot to accurately trigger the 2-camera sensor when at a desired location.
The study area was located at Watts Bridge Memorial Airfield, near Toogoolawah (152.460º, -27.098º) in South East Queensland, Australia. The airfield has dedicated areas for use of remotely controlled aircraft, with the mission being undertaken on 5 March 2008.
The target and waypoints were arranged so that the UAV flew in an anti-clockwise flight pattern. Three separate missions were flown with images being acquired when over target on each of the nine passes. Although capturing the target in the image was achieved on every flight, the accuracy of capturing the target in the middle of the image was variable. The offset from the centre of the image to the target (zero in the perfect system) ranged from just under 15 to just over 60 % of the image extent. The misalignment was due to a combination of cross-wind, GPS / autopilot error, the UAV not being level when the image was acquired, and / or inaccuracies in positioning the sensors in the hinged pod.
The capacity to accurately acquire images over pre-determined points is essential to ensure coverage and to expedite mosaicing of the images. It will also expand the application of these technologies into the broader-scale applications, such as imaging in broadacre cereal cropping or imaging along transects.